I haven't seen this answered here before; I have a '71 Malibu with Sweep Dash. I'm planning on pulling and replacing the whole dash for a cleaner one (still Sweep).

Since I'm going in there, does it make sense to replace the underdash harness while in there? I'm hoping to do this over 2-3 days. The original harness SEEMS fine, but it is old and worn. I have never done either before, but I think I can handle it if I take good notes and photos when it all comes apart (plus I have the manuals).

(Also - the car is an A/C model, and the A/C has it's own harness, right? Do I need bother with this one too?)

imo if it still good i would leave it in, most of the wiring in there is plug and play and getting the dash out is not that bad, the ac venting will be more trouble after 30+ years is going to be very tender and brittle just be carefull and you should be fine:yes:

Yes the A/C harness is separate but it does plug into the underdash harness for power.

Yes. Already been "back there" and the A/C ducts were shot. Already covered most of that with the dash on. Thanks...